The Changing Earth

Rocks, minerals, and soil are always on the move. They are constantly combining, and recombining. These changes take place both above and below the Earth's surface.

The Rock Cycle

The oldest and slowest Earth cycle is rock formation. From deep in the Earth, hot magma rises up. The magma cools and hardens into igneous rock. Over time, weathering forces loosen its surface and carry away rock and mineral fragments. These fragments build up in layers. Eventually the layers cement into sedimentary rock. Its deepest layers face so much pressure and heat that they change into metamorphic rock. When this rock gets hot enough, it melts back into magma. And so the cycle begins again.

Many rock and mineral fragments have an extended stay on the Earth's surface. They become soil particles. In fact, soil gets a fresh supply of rock and mineral fragments all the time. Living organisms also provide the soil with organic matter on a regular basis.

But soil gets lost, too. Natural forces remove soil from an area, at times very quickly. Human activities also destroy soil in different ways. For instance, our buildings and roads sometimes cover over fertile soil. Certain farming techniques harm the soil, too. These methods cause soil nutrients to drain away.

Protect Resources

Rocks, minerals, and soil are important natural resources. Our society makes use of them daily. We crush huge masses of rock for building materials. We dig mines the world over in search of minerals. And we grow crops on millions of acres of farmland.

These valuable resources are here for the taking. But it's up to us to use them wisely.